import math
class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y

def d(p1, p2):
    a = p2.x - p1.x
    b = p2.y - p1.y
    c = math.sqrt(a * a + b * b)
    return(c)

data = [float(i) for i in input().split()]
p1 = Point(data[0], data[1])
p2 = Point(data[2], data[3])
print(d(p1,p2)) import math math class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y Point def __init__(self, x, y):
        self.x = x
        self.y = y __init__ self.x = x self.x self x x self.y = y self.y self y y self self x x y y object def d(p1, p2):
    a = p2.x - p1.x
    b = p2.y - p1.y
    c = math.sqrt(a * a + b * b)
    return(c) d a = p2.x - p1.x a p2.x - p1.x p2.x p2 x p1.x p1 x b = p2.y - p1.y b p2.y - p1.y p2.y p2 y p1.y p1 y c = math.sqrt(a * a + b * b) c math.sqrt(a * a + b * b) math.sqrt math sqrt a * a + b * b a * a a a b * b b b return(c) c p1 p1 p2 p2 float(i) for i in input().split() for i in input().split() i input().split() ().split () input split for i in input().split() float(i) float i data = [float(i) for i in input().split()] data [float(i) for i in input().split()] p1 = Point(data[0], data[1]) p1 Point(data[0], data[1]) Point data[0] data 0 data[1] data 1 p2 = Point(data[2], data[3]) p2 Point(data[2], data[3]) Point data[2] data 2 data[3] data 3 print(d(p1,p2)) print d(p1,p2) d p1 p2 data = [float(i) for i in input().split()] [float(i) for i in input().split()] data p2 = Point(data[2], data[3]) Point(data[2], data[3]) p2 class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y Point def d(p1, p2):
    a = p2.x - p1.x
    b = p2.y - p1.y
    c = math.sqrt(a * a + b * b)
    return(c) def d(p1, p2):
    a = p2.x - p1.x
    b = p2.y - p1.y
    c = math.sqrt(a * a + b * b)
    return(c) d p1 = Point(data[0], data[1]) Point(data[0], data[1]) p1
import math
class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y

def d(p1, p2):
    a = p2.x - p1.x
    b = p2.y - p1.y
    c = math.sqrt(a * a + b * b)
    return(c)

data = [float(i) for i in input().split()]
p1 = Point(data[0], data[1])
p2 = Point(data[2], data[3])
print(d(p1,p2))
